Antenna



May 19, 1942.

R. M. WILMOTTE ANTENNA Filed May 8, 1941 I 2 Sheets-Sheet 1 BY W ATTORNEY y 19, 1942- R'. M. WILMOTTE 2,283,617

ANTENNA Filed May 8', 1941 2 Sheets-Sheet 2 INVENTOR TTORNEYV Patented May 19, 1942 UNITED STATES PATET OFFICE ANTENNA Raymond M. Wilmette, Washington, D. 0. Application May 8, 1941, Serial 'No. 392,439 (Cl. 250 33) 2 Claims.

My present invention-concerns radiators of electro-magnetic waves and in particular, methods of and means for controlling the radiation patterns from a radio antenna or the like.

One object of my present invention is to provide means for predetermining the radiation pattern from a radio antenna.

Another object is to provide methods of and the radiation pattern of an antenna in a simple and efiicient manner.

Still another object is to provide methods of and means for obtaining an optimum relation between radiation pattern and antenna efliciency.

A further object is to control the impedance characteristics of an antenna from a remote point. a

These and other. objects will be evident from the detailed description of the invention given in connection with the various figures of the drawings.

It has long been tribution in a vertical radiator of approximately of the radiator and the current distribution along the radiator and its ground system.

In the past it has been the practice to excite single vertical radiators at or near the base ex- According to the present s excited ts length invention, a radiator or fed at one or more points along and the ratio and phase of the various iii feed at an intermediate point still iting' currents is controlled in order to control distribution pattern exc the at a remote point as, for instance, from the base of the radiator.'

In the drawings:

Fig. 1 shows a two section antenna fed at a point remote from its base and with the base grounded.

Fig. 2 shows an antenna Fig. 1 but with its base ungrounded.

Fig. 3 shows an antenna similar to that of Fig. .2 but with an impedance connected between the base and ground.

Fig. 4 shows a two section antenna fed with currents of predetermined phase between the secons and between Fig. 5 shows a two section antenna fed between the sections of the lower section. V

Fig. 6 shows a two section antenna fed between the lower section and ground and with a remote impedance connected between the section.

Fig. 7 shows a form of top loading on an antenna.

Fig. 8 shows another form of top loading on an antenna. 7

Fig. 9 shows curves. of current distribution along an antenna according to the present invention.

"top loading. The lower section its base to ground 4. The antenna is fed thru a coupling net-work such as from secondary 5 its base improved radiation patterns are possible. By the employment of top loading and a signal further consimilar to that o1v former 4543 as shown in sulated by means of insulator I placed between lower section 2 and ground 4. The application of an isolating and coupling means such as trans- Fig. to the structure of Fig. 2 to prevent the transmission line from short-circuiting insulator II] will be apparent to those skilled in the art. The insulation of lower section 2 and the distance between insulator I0 and ground 4 provides still further control of the radiation pattern of the antenna system.

Fig. 3 shows a variation of the antenna system of Fig. 2, wherein across base insulator I0. Impedance I! may be a positive or negative reactance or a more or less complex impedance depending on the effect desired on the current phase, distribution and magnitude in the radiating structure and in turn on the radiation pattern.

Fig. 4 shows another variation of the basic double insulated radiator of Fig. 2. In Fig. 2 signals or energy to be radiated is fed across both insulators 3 and nitude of the energy fed across insulator 3, i. e. between sections I and 2 may be controlled by a phase and amplitude control box I6. The energy fed across insulator I!) i. e. between antenna section 2 and ground 4 may be applied by means of transmission line I4-I5 and isolating transformer I2-I3 and its phase and magnitude may be controlled by means of phase and amplitude control box I1. It will be evdent to those skilled in the art that a wide range of control of the radiation pattern may be the lengths of antenna sections I and 2, the distance between section 2 and ground and the relative phase and magnitudes of the voltages fed across insulators 3 and Ill. The relative phase and magnitude of the voltages fed across insulators 3 and I0 may be controlled by means of variable electrical circuit elements after the type of radiator.

Fig. 5 shows another variation of the present invention in which in addition to the remote excitation across insulator 3, the lower section 2 is shunt fed from transmission line I8-I9 and the relative phase and magnitude of the two exciting currents is controlled by phase and amplitude control box 20 connected between transmission lines 1-8 and I8--Il. The radiation pattern may be varied by varying the lengths of sections I and 2, the point I1 at which the shunt feed to section 2 is made and the relative phase and magnitude of the two exciting voltages.

Fig. 6 shows an antenna system the inverse of the system of Fig. 3 wherein the excitation is applied across lower insulator III by means of transmission line 3Il--3I and isolating transformer 28-29 and an impedance 21 is connected across insulator 3. Impedance 21 may be close connected across insulator 3 or it may be connected by means of lines 23-g-24 and 25-26 and located at a remotepoint for convenience of ad- ID. The phase and magproduced by varying an impedance II is connected I rent distribution justment. Impedance 21 may be a positive or negative reactance or a simple or complex impedance. For instance, the effective height of the antenna may be changed by a control located at its base.

Isolating means such as transformer 45-46 should be ut'lized in any of the systems of Figures 1, 2, 3, 4, 5, or 6 in case it is necessary to prevent the transmission line from short-circuiting an insulator.

Fig. 7 shows a form of top loading in which capacity is added to radiator section I by means or an added conductor formation as for instance that of conductors 32-33-34.

Another form of top loading is shown in Fig. 8 wherein portions of guy wires 35 and 36 insulated at a desired distance from the top of section I by means of insulators 31 and 38.

Many other forms of top loading will be apparent to those skilled in the art within the spirit and scope of the present invention.

Fig. 9 shows a two section antenna I-2 with insulator 3 separating the sections and insulator In between lower section 2 and ground. If insulator 3 were shorted and energy were fed to the lower end of section 2, the usual current distribution along the antenna would be as shown by curve 40. However, according to the present invention a current distribution as shown by curve 43 may be obtained. Evidently a wide range and variety of current distributions may be obtained by means of the various antenna combinations described above according to the present invention.

Fig. 10 shows a radiation pattern in a vertical plane. At 42 is shown a pattern due to thecurof Fig. 9 and 44A and NB the pattern due to distribution 43. This comparison shows clearly the gain along the horizontal and the reduction in vertical radiation.

The curves of Figs. 9 and 10 are not from actual data but are indicative of the results which may be obtained.

Fig. 11 shows a system similar to that of Fig. 2 except that transmission line 1-8 is connected directly to radiator 2 and hence it is necessary to use an isolating transformer 45-46 at the base of'the antenna system to prevent shortcircuiting insulator I0.

While two section antenna systems have been shown and described, it is not intended to limit the invention to any specific number of sections since the use of the invention with any number of sections will be apparent to those skilled in the ar There are many possible applications of the present invention. It may be used to maximize the horizontal radiation or the verticalradiation or the radiation at one or more particular angles to the'horizontal. The invention is useful in obtaining the optimum conditions when some factor such as the height of the antenna is fixed and some other factor such as the horizontal radiation is desired to be a maximum. The invention is particularly useful in obtaining maximum efiiciency of power radiated in a particular direction for a given power input to the system.

Bymeans of the invention it is possible to increase the directivity of radiator without increasing its height, proportion of the total energy radiated in a selected direction. If the directivity is increased considerably, the ,total radiated energy may decrease, but the energy radiated in the selected directionmay increase. Those two efiect'sact in that is transmit a greater The invention may also be employed to produce minimum signal in a desired direction. This condition is sometimes required for instance in broadcasting in the regular broadcast band when it is desired to reduce the strength of the sky wave which leaves the transmitting antenna at some predetermined angle to the horizontal. Reduction of this sky wave may be required to decrease the interference in the voice area of some other station or to reduce the distortion effect which takes place in what is known in the art as the rapid feeding zone where the ground wave and sky wave are of the same general order of magnitude, or to change the location of this zone.

Antennas are well known in the art which are excited at or near the base, as in regular broadcast antennas, or in or near the center as in dipoles and combinations of di-poles as in many antennas used at higher frequencies. The point of excitation has been selected either for convenience, proximity to the source, symmetry of the structure, reducing possible field distortions due to the effect of the feeding transmission line in the radiating field, or for value of the impedance which the antenna has at the point selected to match the impedance of the feeding transmission line and associated circuits. Such antennas have inherent directional properties and impedances have been used in the antenna itself to partially control the directional effect. According to the present invention, when there is only one point feeding, it is selected in order to obtain a predetermined radiation pattern withchanging the overall dimensions of the radiating structure and by adjusting the electrical circuits connected to the antenna to obtain a current distribution in the radiating structure which will produce the radiation pattern sought. Where there is more than one point at which energy is fed to the radiator the points of feeding are selected for the same purpose of controlling the radiation pattern besides which the phase and amplitude relationship of the feeding voltages at the points of feeding are controlled, thus providing an additional way in which the radiation pattern may be controlled.

Some forms of the present invention are distinguished from the usual di-pole antenna in that electrical circuits or a source of signals are con- 7 nected across a break in the antenna by means of a transmission line lying along and usually in contact with a radiating portion of the radiator. This means that the transmission line, as it leaves a feeding point, lies substantially parallel to a radiating part of the radiator and close to it, in its travel to the phasing circuit or transmitter.

What is claimed is:

1. In an antenna system, the combination of, a vertical antenna including an upper section said upper section being aperiodic and a lower section, means for-insulating said two sections from each other, means for insulating said lower section from ground, a source of energy for exciting said antenna, means for applying a portion of said energy between said two sections, means for applying a second portion of said energy between said lower section and ground, and means for varying the relative phases and magnitudes of said two portions of energy whereby to control the current distribution along the length of said lower radiator.

2. In a radio antenna system, a first vertical transmission element for transmitting elec-' trical energy, a second vertical transmission element for transmitting electrical energy, an-- aperiodic electrical loading means adjacent the upper ends of said elements, means coupling said loading means between the upper ends of said elements, a translating means connected to said elements, and means for adjusting the phase and amplitude of the electrical energy trans mitted by said transmission elements relative to the energy at the translating means, one of said transmission elements constituting an antenna, the other of said transmission means comprising a, wire lying closely adjacent said antenna.

RAYMOND M. WILMOTTE. 

